Heat exchanger system

ABSTRACT

A method la proposed for producing a plate heat exchanger with flow channels through which a first and a second medium flow, the flow channels formed for the first medium between individual plates joined together to form a pair of plates, and for the second medium between pairs of plates joined together to form a stack of plates. For a cost-effective production of countercurrent flow plates and cross flow plates within a single manufacturing plant, the individual plates are produced from a non-pressed plate blank, wherein first a tool is converted with exchangeable mold members for producing cross flow plates or countercurrent flow plates, and subsequently, the plate blank is pressed by the converted tool into a cross flow plate or a countercurrent flow plate, thereby forming corresponding edges and/or contact surfaces as well as inflow and outflow cross-sections.

BACKGROUND OF THE INVENTION

The invention relates to a method for producing a plate heat exchanger comprising flow channels through which a first and a second medium flows, which flow channels are formed for the first medium between individual plates joined together to form in each case a pair of plates, and for the second medium between pairs of plates joined together to form a stack of plates, wherein the individual plates and the pairs of plates are connected to each other at edges and/or support surfaces running in each case parallel to the main flow direction, wherein in the main flow direction of the first medium, each individual plate comprises corresponding inflow and outflow cross-sections for the first medium, and in the main flow direction of the second medium, comprises corresponding inflow and outflow cross-sections for the second medium.

Methods for producing plate heat exchangers are well known in the prior art. The plate heat exchangers can be designed as concurrent/countercurrent flow heat exchangers or as cross flow heat exchangers.

Fact is that with a manufacturing line designed for producing concurrent flow plates it is not readily possible to produce also cross flow plates or vice versa. The reason for this is the different structural design of concurrent flow plates and cross flow plates, respectively. Different are in particular position and size of the inflow and outflow cross-sections through which the media flow between adjacent heat exchanger plates. Likewise, countercurrent flow plates and cross flow plates also differ in terms of their dimensions. The heat transfer capacity of concurrent flow plates, for example, is substantially set through the length of the plates. The meaning of the term “countercurrent flow plates” implies here in each case countercurrent flow plates as well as concurrent flow plates. When designing cross flow plates, it is also to be considered that, in contrast to countercurrent flow plates, the first medium flows over the length of the plate while the second medium flows over the width of the plate. Thus, when designing cross flow plates, it is particularly important to match the width of the plate with its length or vice versa. Ideally, cross flow plates have an almost square shape.

Overall, the production of cross flow plates or concurrent flow plates faces conflicting requirements which are a result of the necessary constructional features of the respective individual plate. In the case of countercurrent flow plates it is in particular desired for manufacturing-related reasons that said plates have a fixed plate width. In this way, they can be integrated, in a simple manner in the manufacturing sequences. The necessary dimensioning for a particular heat transfer capacity is carried out via the length of the plates. Thus, with a predetermined width, plates with different lengths can be produced depending on the requirements for the heat transfer capacity. However, in the case of cross flow plates, other parameters have priority. Since the heat media flow from different directions on the front and rear side of the cross flow plates, it is necessary to configure the individual plate such that measures are taken which substantially equalize the heat transfer coefficient on both sides of the plate surface area. In the prior art, equal heat transfer coefficients are ensured in that plate width and plate length are matched with each other. This is required because the one medium flows along the length of the plate while the second medium flows across the width of the plate. These conflicting requirements are responsible for the fact that the production parameters and methods for producing countercurrent flow plates cannot be applied to cross flow plates or vice versa.

Likewise, the inflow and outflow cross-sections of countercurrent flow plates and cross flow plates are designed differently. This relates to their position, on the respective individual plate and also to their size. Since in the case of countercurrent flow plates the first and the second medium flow in the same or opposite direction, it is necessary for space reasons to provide in each case only half the plate width as inflow or outflow cross-section. In contrast, this problem does not exist for cross flow plates because the inflow and outflow cross-sections of the two plate sides are offset to each other by 90°. Thus, also on this issue, there is no possibility to apply the manufacturing principles known from countercurrent flow plates to the production of cross flow plates. Furthermore, a different structural design for countercurrent flow plates and cross flow plates is given in that due to the different positions of the inflow and outflow cross-sections, the position of the edges and contact surfaces is also different. Since in the case of cross flow plates, each of the four plate edges is provided on the front side or the rear side of the individual plate with inflow and outflow cross-sections, respectively, the principle of connecting two individual plates so as to form a pair of plates, or connecting a plurality of pairs of plates so as to form a stack of plates cannot be transferred from the countercurrent flow plate to the cross flow plate.

Overall, ail these constructional differences result in different dimensions of the individual plates and in other positions and dimensions of the inflow/outflow cross-sections, and also in each individual case in a completely different dimensioning for achieving a desired heat transfer coefficient or a heat transfer coefficient that is the same on both sides of the plate surface area.

It is therefore an object of the present invention to provide a method for producing a plate heat exchanger, which method enables producing countercurrent flow plate heat exchangers as well as cross flow plate heat exchangers.

SUMMARY OF THE INVENTION

This object is achieved according to the invention in that the individual plates are produced, in each case from a non-pressed plate blank, wherein first a tool is converted with exchangeable mold members for producing cross flow plates or countercurrent flow plates, and subsequently, the plate blank is pressed by means of the converted tool into a cross flow plate or a countercurrent flow plate, thereby forming corresponding edges and/or contact surfaces as well as inflow and outflow cross-sections.

The central idea here is to be able to use, with as little retrofitting effort as possible, the manufacturing plants designed, for example, for producing countercurrent flow plates and also for producing cross flow plates. In particular, the pressing tools used for producing countercurrent flow plates are retooled through simple and in particular inexpensive modifications in such a manner that these tools are also suitable for producing cross flow plates. The basic configuration of the heat exchanger plates remains unchanged so that plate blanks for the production of countercurrent flow plates can also be used for producing cross flow plates. Based on a modular design principle, the tool used can be provided with exchangeable mold members so that only the mold member suitable for producing countercurrent flow plates or cross flow plates has to be attached onto the tool. The mold member used serves for pressing the plate blanks at the edges and the contact surfaces or the inflow and outflow cross-sections. If after producing countercurrent flow plates, it is now intended to change over to cross flow plates in the same manufacturing plant, the only thing necessary is to attach, the mold member suitable for cross flow plates onto the tool which forms the inflow and outflow cross-sections at the position suitable for cross flow plates. Moreover, the plate blanks remain the same, regardless of whether the heat exchanger plates are to be produced for cross flow plate heat exchangers or countercurrent flow plate heat exchangers. This means in particular also that the dimensions of the plate blanks can remain the same. Otherwise, the problem would arise that the plate blanks used for cross flow plates could not be integrated in a manufacturing plant for countercurrent flow plates. The further features of the heat exchanger plates do not depend on the question whether the plate is later used as a cross flow plate or as a countercurrent flow plate. This relates in particular to a knob structure implemented thereon, alternating plate supports for supporting the heat exchanger plates arranged next to each other, or the plate thickness.

Overall, the invention results in a simplified method for producing cross flow plate heat exchangers and also countercurrent flow plate heat exchangers, which method does not require two separate manufacturing plants for cross flow plates and countercurrent flow plates, but uses a single manufacturing plant for producing both types.

The invention further provides that the individual plates are cross flow plates, wherein the cross flow plates are positioned at such a distance from each other that with regard to the first and the second medium, substantially identical heat transfer coefficients are obtained on both sides of a cross flow plate.

In terms of yield, cross flow plates are less effective than countercurrent flow plates, therefore, when using a cross flow plate, the plate blank of which has the dimensions of a countercurrent flow plate, special measures have to be taken in order to increase efficiency. For this, varying the distances between adjacent cross flow plates is suitable to set substantially identical heat transfer coefficients on both sides of the plate surface area. This offsets the disadvantage that the cross flow plates according to the invention cannot be produced in any desired width, because it must still be possible to integrate them in a manufacturing plant for producing countercurrent flow plates. Thus, with regard to the use as cross flow plates, one degree of freedom is missing for carrying out an optimized configuration of plate blanks previously used only for producing countercurrent flow plates. In order to compensate this disadvantage, the flow cross-section, which results from the distance between two adjacent individual plates, is adjusted. In the course of this, the plate spacing is reduced resulting in an increased flow velocity. In this manner, a cross flow heat exchanger is created which has differently configured flow-cross-sections with regard to the media conveyed therethrough.

It is in particular useful that the distance between adjacent individual plates is determined by the length of knobs arranged on one or both individual plates. Said knobs serve as spacers between two adjacent individual plates so that by simply imprinting more or less deep knobs, the distance can be variably adjusted. With regard to manufacturing, the depth of the knobs can be implemented in a simple manner because the only important thing in terms of tooling is to use suitable knob punches. Furthermore, this does not involve an additional work step to be carried out because the knobs are provided on the individual plates in any case so as to serve as flow-distributing devices.

Furthermore, adjusting different plate distances on opposing sides of the individual plates has the advantage that the flow cross-section for a heat medium enriched with foreign particles or dirt particles, which can be, for example, flue gas from a waste incinerator, can be formed adequately large so that the risk of contamination due to adhesion is reduced. In this respect, the missing degree of freedom with regard to the plate width is completely offset in that the production is simplified and, moreover, the free adjustability of the plate distances results in an additional advantage.

The invention further provides that on the individual plate, one or a plurality of separation embossments are provided which run parallel to the main flow direction of the medium. Due to the flow channels between adjacent cross flow plates, which channels run differently compared to countercurrent flow plates, a sub-division of the plates can be carried out by means of separation embossments. This results from the fact that the media flow in each case over the entire plate width of the cross flow plate, whereas in the case of the countercurrent flow heat exchanger, the media are introduced only through one plate half. The formation of separation embossments is optional. It is also possible to provide plates without separation embossments.

However, subdivision through separation embossments can be carried out for two different reasons:

On the one hand, subdividing the individual plate by means of one or a plurality of separation embossments can provide a loop-like recirculation mode in which the inflowing medium flows over the heat exchanger plate only on one side of the separation embossment, then, upon reaching the opposing plate edge, undergoes a 180° change of direction, and subsequently flows one more time over the width of the plate, but this time on the other side of the separation embossment, so that it flows in the opposite direction. With a single separation embossment on each side of the plate it is achieved that the medium flows twice through the plate. However, it is also possible that a plurality of separation embossments is provided on a side of the plate so that the medium runs multiple times across the width of the plate. This results in a meander-shaped flow of the medium within the individual plate. Through the number of separation embossments used, not least the heat transfer coefficient for an individual plate can be adjusted.

On the other hand, separation embossments can also be used to change the flow pattern of the flow passing through an individual plate. Depending on how many separation embossments are used and at which distance from each other they are arranged, the flow can be conditioned such that it runs in the unstirred state through the plate. In order to achieve this, a particularly close guidance of the medium, between the separation embossments has to be implemented. If a plurality of separation embossments is used with a clearance therebetween as small as possible, an unstirred flow can be successfully maintained.

With the formation of separation embossments it is also possible to achieve a loop-like recirculation mode and, at the same time, to maintain an unstirred flow. Thus, both parameters can be combined with each other so as to utilize the advantages of both variants and, as a result, to improve the heat transfer capacity of the heat exchanger and/or to equalise the heat transfer coefficient on both sides of the plate. In both cases, separating individual regions of the plate from each other is achieved through a simple embossment which, in terms of tooling, can be implemented in a particularly simple manner. Thus, instead of knob punches, the tool can comprise a continuous pressing bar made of metal so that without significant effort, a tool is provided, which, besides embossing knobs, also forms a suitable embossment for the separation embossments.

The invention further proposes a pressing tool for pressing individual plates for plate heat exchangers, characterized by a plurality of exchangeable mold members which comprise mold members for producing cross flow plates as well as mold members for producing countercurrent flow plates. Thus, a modularly structured pressing tool is obtained which can receive different mold members including mold members for producing cross flow plates as well as mold members for producing countercurrent flow plates. Thus, changing over the production from countercurrent flow plates to cross flow plates is made easy.

The invention further proposes a system for producing individual plates for plate heat exchangers, with a plurality of plate blanks of predetermined width suitable for producing countercurrent flow plates as well as cross flow plates, and with a pressing tool having a plurality of exchangeable mold members which comprise mold members for producing countercurrent flow plates as well as mold members for producing cross flow plates. With this system, cross flow plates for cross flow plate heat exchangers can be produced in a simple and cost-effective manner from plate blanks which are originally intended for the production of countercurrent flow plates.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages of the invention are illustrated in more detail hereinafter by means of the figures. In the figures:

FIG. 1 shows a perspective view of a stack of plates formed from a plurality of individual plates;

FIG. 2 shows a top view of an individual plate according to the invention;

FIG. 3 shows a schematic view of a plate heat exchanger with cross flow plates.

DESCRIPTION OF PREFERRED EMBODIMENTS

The exemplary embodiment of a plate neat exchanger made of countercurrent flow plates schematically illustrated in FIG. 1 shows perspectively a plate stack S from a plurality of individual plates 1 which are in each case connected to each other so as to form a pair P of plates. Each individual plate 1 comprises a bottom 11, edges 12, contact surfaces 13 and transverse edges 14 a, 14 b. The contact surfaces 13 are offset in height with respect to the edges 12. The offset between the contact surface 13 and the associated edge 12 is twice as large as the offset between the edges 12 and the bottom 11 of the individual plate 1. Accordingly, the bottom 11 lies in the middle of the height between the plane of the edges 12 and the plane of the contact surfaces 13. In the exemplary embodiment, the transverse edges 14 a, 14 b running transverse to the edges 12 of the individual plate 1 lie approximately half in the plane of the edges 12 or in the plane of the contact surfaces 13, respectively, FIG. 1 shows that here the transverse edges 14 a and 14 b oppose each other diagonally.

In each case two of the individual plates 1 illustrated in FIG. 1 as the uppermost part are connected according to the bottom illustration in FIG. 1 so as to form pairs P of plates. FIG. 1 exemplary illustrates five complete pairs P of plates, wherein on top of the uppermost pair of plates, an additional individual plate 1 is arranged which is also connected to the uppermost individual plate 1 shown spaced apart so as to form a pair P of plates.

Connecting the pairs P of plates in the region of the contact surfaces 13 so as to form a plate stack S results in channels arranged on top of each other for the two media involved in the heat exchange. While the one medium flows in the flow channels which are formed in each case by the pairs F of plates, the other medium flows in the flow channels which are formed by joining the pairs P of plates together so as to form the plate stack S. Here, the individual plates ' 1 transverse edges 14 a lying in the plane of the edges 12 form, the inflow cross-section Z1 or, respectively, the outflow cross-section A1 of the flow channels for the medium flowing between the pairs P of plates. The individual, plates' 1 transverse edges 14 b extending in the plane of the contact surfaces 13 form the inflow cross-sections Z2 or, respectively, the outflow cross-sections A2 for the other medium which flows between the individual plates 1 of each pair P of plates in the same direction or in the direction counter to the first medium. FIG. 1, which shows a countercurrent heat exchanger, illustrates that due to the diagonal arrangement of the inlet and outlet openings, the inflow cross-sections Z1 and Z2, respectively, for the one medium are located next to the outflow cross-sections A2 and A1, respectively, for the other medium, namely offset in each case by half the height of a pair P of plates.

FIG. 2 shows an individual plate 1, the inflow cross-section Z1 of which extends over half the width of the individual plate 1, from the longitudinal center up to the longitudinal edge 12. The individual plate 1 has a turbulence-generating profiling 31, 32 which extends over the entire width of the individual plate up to the contact surfaces 13. Said profiling 31, 32 consists of a high number of knobs 31, 32 embossed info the individual plates 1.

FIG. 3 illustrates a cross flow plate heat exchanger consisting of individual plates 1 (cross flow plates) arranged next to each other. Each cross flow plate 1 has two corresponding inflow and outflow cross-sections Z1, A1 (not illustrated in FIG. 3) and two corresponding inflow and outflow cross-sections Z2, A2 arranged, offset thereto by 90° on the opposing side of the individual plate 1. In the plane of projection, the opposing side of the individual plate 1 is behind the illustrated cross flow plate. Furthermore, knobs 81, 32 are attached, on the individual plate 1, said knobs serving for distributing the medium over the entire extension of the individual plate 1, On the individual plate 1 illustrated in the image plane at the very front, furthermore, there is a separation embossment 2 which divides the plate 1 in two preferably symmetrical halves. Overall, the cross flow plate heat exchanger is configured such that the first medium flows into the space between the illustrated plate stack P of individual plates 1 and the individual plate 1 exemplary illustrated in the front of the image plane, while the second medium flows through the plate 1 illustrated individually on the front side. Here, the first medium flows in the image plane from top down while the second medium passes through the plate 1 from left to right, makes a 160° turn there, and subsequently flows again from right to left through the plate 1.

The method according to the invention for producing a plate heat exchanger from individual plates 1 according to the invention is carried out such that, for example, the operator of a manufacturing plant for countercurrent flow plates varies the pressing tool used by him/her in such a manner that the tool is provided with exchangeable mold members suitable for producing cross flow plates. Thereafter, the plate blanks usually provided for producing countercurrent flow plates are pressed by means of the varied tool thereby pressing the inflow and outflow cross-sections Z1, Z2, A1, A2 at the positions where they are required for forming a cross flow plate. Furthermore, by means of an adequate pressing tool, the individual plate 1 is provided with knobs 31, 32 which are substantially distributed over the entire plate 1. In addition, these knobs 31, 32 are dimensioned in terms of their length in such a manner that they serve as spacer between two adjacent individual plates 1. The spacing is regulated through the length of the knobs 31, 32 in such a manner that a suitable flow cross-section between adjacent individual plates 1 is created which is suitable to set the heat transfer coefficient of the two heat media to substantially the same value on opposing sides of the plate.

Furthermore, the tool can be provided with a mold member for forming a separation embossment 2 by means of which one or a plurality of separation embossments 2 can be pressed into the individual plate 1. These separation embossments 2 serve for dividing the individual plate 1 into a plurality of segments running parallel to the flow direction of the medium, wherein, on the one hand, said segments prevent the medium from being turbulently mixed and therefore enable an unstirred flow, and/or, on the other, said segments serve for creating a plurality of segments on the individual plate 1, in which segments the heat medium can be directed back and forth in opposite directions, wherein the medium passes through one or a plurality of 180° turns. In this manner, the performance of the plate heat exchanger can be significantly increased.

The specification incorporates by reference the entire disclosure of European priority application 12 170 500.8 having a filing date of Jun. 1, 2012.

LIST OF REFERENCE CHARACTERS

A1 Outflow cross-section

A2 Outflow cross-section

P Pair of plates

S Stack of plates

Z1 Inflow cross-section

Z2 Inflow cross-section

1 Individual plate

2 Separation embossment

11 Bottom

12 Edge

13 Contact surface

14 a Transverse edge

14 b Transverse edge

31 Knob

32 Knob 

What is claimed is:
 1. A method for producing a plate heat exchanger comprising flow channels through which a first and a second medium flows, which flow channels are formed for the first medium between individual plates (1) joined together to form in each case a pair (P) of plates, and for the second medium between pairs (P) of plates joined together to form a stack (S) of plates, wherein the individual plates (1) and the pairs (P) of plates are connected to each other at edges (12) and/or support surfaces (13) running in each case parallel to the main flow direction, wherein in the main flow direction of the first medium, each individual plate (1) comprises corresponding inflow and outflow cross-sections (Z1, A1) for the first medium, and in the main flow direction of the second medium, comprises corresponding inflow and outflow cross-sections (Z2, A2) for the second medium, the method comprising: producing the individual plates (1) from a non-pressed plate blank by first converting a tool with exchangeable mold members to a converted tool adapted to produce cross flow plates or adapted to produce countercurrent flow plates and, subsequently, pressing the plate blank with the converted tool into a cross flow plate or a countercurrent flow plate, thereby forming corresponding edges (12) and/or contact surfaces (13) as well as inflow and outflow cross-sections (Z1, Z2, A1, A2).
 2. The method according to claim 1, wherein the individual plates (1) are cross flow plates, wherein the cross flow plates are positioned at such a distance from each other that with regard to the first and the second medium, substantially identical heat transfer coefficients are obtained on both sides of a cross flow plate.
 3. The method according to claim 2, wherein the distance between adjacent individual plates (1) is determined, by the length of knobs (31, 32) arranged on one or both individual plates (1).
 4. The method according to claim 1, wherein on the individual plate (1), one or a plurality of separation embossments (7) are provided which run parallel to the main flow direction of the medium.
 5. A pressing tool for pressing individual plates (1) for plate heat exchangers, the pressing tool comprising a plurality of exchangeable mold members, the mold members including first mold members for producing cross flow plates as well as second mold members for producing countercurrent flow plates.
 6. A system for producing individual plates (1) for plate heat exchangers, the system comprising a plurality of plate blanks of predetermined width suitable for producing countercurrent flow plates as well as cross flow plates, and further comprising a pressing tool having a plurality of exchangeable mold members, the mold members including first mold members for producing cross flow plates as well as second mold members for producing countercurrent flow plates. 